Remote-control system



July 18, 195o P. w. NOSKER 2,515,254

REMOTE CONTROL SYSTEM DTI /4 25 c25 0 1:33

BYWLD/ F. W. NOSKER REMOTE CONTROL SYSTEM July 1s, 195o 7 Sheets-Sheet 2 Filed Dec. 11, 1946 July 18, 1950 P. w. NosKr-:R

REMOTE CONTROL SYSTEM Filed Dec. 11, 194e 7 Sheets-Sheet 5 O rm SON NWN NIWN

July 18, 1950 P. w. NOSKER REMOTE CONTROL SYSTEM 7 Sheets-Sheet 4 Filed Deo. l1, 1946 'i INVENTOR.

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Ffm ,w A05/ef@ July 18, 1950 P. w. NosKER REMOTE CONTROL SYSTEM 7 Sheets-Sheet 5 BY WW Filed Dec. 1l, 1946 July 18, 1950 Filed ,.Dec. 11, 1946 P. W. NOSKER REMOTE CONTROL SYSTEM '7 Sheets-Sheet 6 P. W. NOSKER REMOTE CONTROL SYSTEM July 1s, 195o Filed Dec. ll, 1946 7 Sheets-Sheet '7 NAN INVENTOR. Pi/ I4. /VJA .6

Patented July 18, 19540 UNITED STATS PAT-ENT GFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. '757) 4 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes Without payment to me of any royalty thereon.

This invention relates to a remote control system for aircraft, guided missiles and the like.

In the past, various systems have been used for controlling remotely aircraft and the like. It is conventional practice when controlling target aircraft, guided missiles, and test aircraft engaged in hazardous missions, to employ an automatic pilot and other automatic devices on the aircraft to maintain preset flight conditions, including predetermined variations of those conditions, such conditions being maintained by the automatic equipment in the absence of radio or other controlling signals from remote points. Remote control of such vehicles has been exercised by transmitting and receiving radio signals operating upon various elements of the automatic control systems. In the arrangements of the kind just described as belonging to the present conventional art, it will be observed that the vehicle or aircraft is actually controlled by the automatic mechanisms installed in it, and the received remote-control signals serve merely to readjust or to alter the manner of response of such automatic control devices. It is correct to say that the so-called remo-te control systems of this type are really automatic control systems that are subject to resetting by remote control.

Remote control equipment, as at present provided and used, imposes limitations of major consequence wherever a high degree of maneuverability is required. Such remote control systems are of the on-off or impulse type in which one or more of separately distinguishable signals may be transmitted at the discretion of the remote operator. When any given signal is transmitted, it causes a relay to close at the receiving station on the mobile vehicle or aircraft and thereby initiates an operation which continues as long as that particular signal is transmitted. The extent or distance to which that particular operation progresses depends upon the length of time of transmission of the particular controlling signal involved. In consequence, the remote pilot or the operator in present-day conventional practice manipulates push buttons or switches which are not similar to conventional airplane controls and further, the remote pilot or operator has no direct control over the motions of the elevator, rudder, or ailerons on the aircraft. Furthermore, conventional systems have inherent time lags which are highly undesirable when abrupt or extensive maneuvers must be performed.

The present system of remote control is intended for and is particularly adapted to the flight testing of military ,aircraft or missiles lto extreme limits of airspeed, acceleration or other flight parameters. The present remote control system is intendedto be suiiciently versatile to permit attainment of every -flight condition and attitude of which an ,airplane or missile is capable.

In consequence of the fact that these objectives seem Yto be unattainable by the usual remote control systems yor their ordinary modifications, I have provided a system which is diiferent from the conventional in the following respects:

a. The desired maneuvers of the missile or the like and their manner of execution are less limited by my system of r-emote control than by the characteristics of the missile or other aircraft, itself.

b. The remote control system which vI have provided will work well in any controlled airplane or guided missile -having airplane-type controls, regardless of the peculiarity of the flight characteristics of that airplane or missile.

c. The remote control system is a natural one in which the remote pilot or operator performs his usual functions in the accustomed manner.

d. A proportional control system is incorporated, by which received signals establish directly the position of each control -element on the con` trolled aircraft.

e. The total system preferably includes two separate television channels by which the human pilot in a simulated cockpit in the remote control station receives an image of the forward view from the controlled airplane or missile and an image of an instrument panel on the controlled airplane. In this way, it may be said that 'the remote control pilot actually flies the aircraft or missile being flown by remote control on instruments in the same manner that he would do if he were situated on that controlled aircraft. It istherefore possible to perform safely the first ights of an aircraft under full remote control` One object of ,thepresent invention is to provide larremete control apparatus which is not de.- pendent upon orsensitive to the particular ilying characteristics of the aircraft to be controlled. When suchla system is provided, the remote control receiving systemcan be transferred from one aircraft to another andwill function Wellin any flying vehicle having effective controls provided the Vcontrol limitsarefirst suitably which can function throughout a full 360 ofv either roll or pitch. Present-day gyroscopic automatic pilots of the attitude or position type are unable to function throughout such a complete range.

A fourth object is to provide a system in which the positioning of a control on a power-driven controlled aircraft by a signal receiving station A mounted thereon is dependent upon relative amplitudes of frequencies of two different signals simultaneously transmitted from a signal transmitter station, the amplitude ratio of the two signals being variable at the will of the operator at the transmitting station.

This application is a continuation-in-part of my pending application, Serial No. 494,462, led July 13, 1943, entitled An Aerial Torpedo which has been issued as Patent No. 2,379,469.

In the drawings:

Fig. 1 is a block and schematic diagram of a circuit at a signal transmitting station;

Fig. 2 is a block and schematic diagram of a control-operating circuit at a signal receiving station for receiving and operating controls in response to signals radiated from the signal transmitting station shown in Fig. 1

' Fig. 3 is a block and schematic diagram of a modied circuit for the signal transmitting station; Y i Fig. 3a is a plan view of one form of the transfer switch I2l Fig. 4 is a block and schematic diagram of another embodiment of a circuit for the signal receiving station adapted to be used with the transmitter station circuit Which is shown in Fig. 3;

Fig. 5 is a lateral elevation of a servomotor and a sectional elevation of a gear train housing showing a gear train and a position-selecting potentiometer in section therein and a power take-off disposed outwardly oi the housing and operated by the gear train;

Fig. 6 is a diagrammatic elevation of the potentiometer shown in Fig. 5;

Fig. 7 is a block and schematic diagram of another embodiment of the circuit at the signal transmitting station with setting indicating means and with a trim control as parts thereof;

Fig. 8 is a block and schematic diagram of another embodiment of the receiving station circuit shown in Fig. 2;

' Fig. 9 is a block and schematic diagram of the circuit of a transmitter station similar to that shown in Fig. 1 with the difference that it is made to radiate light waves instead of radio waves;

Fig. 10 is a block and schematic diagram of a control receiving station similar to that shown in Fig. 2 with the difference that it is responsive to light waves instead of tc radio waves; and

Fig. 11 is a block and schematic diagram showing the over-all system and the interrelations between the control and controlled stations, espe-y cially the relations of the radiant energy channels to the remote pilot or operator.

In Fig. 11, is the missile, airplane or other control station. 1l is the ground or mobile control station which may be airborne. A television camera 102 is located within the missile, preferably in the nose, where it may have a clear View ahead. Its output is delivered to a television transmitter 153 from whence it is beamed or broadcast from an antenna 101 to the control station 15H. A second television camera 154 is disposed to view an instrument board 105, the dials of which show the flight and operating conditions aboard the missile 150. The output of camera 156i is delivered to a television transmitter 106, from whence it is beamed or broadcast from an antenna lta to the control station 1G I. A receiving system 108 is provided with an antenna 159 and is connected to actuate the missile flying controls 1I I.

In the control station 19|, an antenna 1I2 intercepts signal from the television transmitter 153 and a second antenna H3 intercepts signal from the television transmitter 166. Television receivers 1li and 1I5 are connected to antennas 1I2 and 'I I3, respectively, and kinescopes 'I I5 and 1I1 are connected respectively to television recevers 1I@ and 1I5. A pilots seat 1I8 is disposed within easily visible range of the kinescopes and within conventional distance and position from pedals 1I9 and 12|] for actuating the rudder. A conventional control stick 12| is provided for aileron and elevator functions. Pedals 1I9 and 120 and stick 12I are each connected to a transmitting system 122 which is arranged to radiate signal from antenna 123. The signals shown as being radiated from antenna 123 may be either radio or other radiant light waves. Appropriate receivers in the control station are used in each case.

Referring to Fig. l, a control station indicated in Fig. 11 as control station 10| is shown and has five signal generators II, I2, I3, Iii, and I5, each signal generator producing electrical impulses which may be pure sine waves, these being of constant amplitude and each having a diierent constant frequency. The outputs of the signal generators II, I2, I3, and I4 are fed to variable attenuators or potentiometers I1, I8, and I9, respectively, and then through ampliiiers 20, 2|, 22, and 23, which are respectively connected in parallel to leads 2t and 25. The output of the signal generator I5 is fed through a xed attenuator 26 and amplifier 21 to leads 24 and 25. Leads 24 and 25 provide input for a modulator 28 which is connected through leads 29 and 30 to a radio transmitter 3I having the usual connections with an antenna 32 and a ground 33 so that the signals may be impressed upon a radio frequency carrier wave for transmission into space.

Fig. 1 is intended to show the basic transmission circuit at the transmitter station. lThe dashed lines 124, 124 in Fig. 1 represent mechanical linkages between the control stick 121 and the pctentiometers I5 and I1. Dashed lines 125 and 125 represent a mechanical linkage between the rudder pedals H9 and 12D and potentiometer I8. Dashed lines 126 represents a mechanical linkage between a throttle control and the potentiometer I9. The relation of these controls to the transmitter is indicated in Fig. 1l with the exception that the throttle control is not shown.

Fig. 2 shows a circuit at the control station or missile indicated as 100 in Fig. 11. Receiving antenna 4D at the control station is coupled toa radio receiver 4I having a ground 42. Receiver 4I is connected by leads 43 and 44 to band pass lters 45,46, All, 48, and 49, arranged in parallel. The band pass filters 45 to 49, inclusive, are tuned to pass signals of the respective frequencies of the signal generators ii to I5, inclusive. Combined signals received by the antenna li), after demodulation by a receiver di, are separated or channeled by the band pass filters 45 to 15, inclusive, and are then amplined by amplifiers 50, 5 I, 52, 53, and 54, respectively, which are connected to the band pass iilters. Other irreversible and linear devices may be used in place of amplifiers. If desired, ampliiiers may be used also on the receiving sides of the hand pass filters. The outputs of the several amplifiers 5S to 55, inclusive, are delivered to rectifiers 55, 55, 5i, 55.3, and 55, which are here shown as of the full-wave dry-disc type. Rectiflers 55, 55, 5l and 53 are each directly connected to a xed load circuit, here represented by resistances SU, 6l, 52, and 63. respectively. The resistances Sil to d3, inclusive, are connected in series with the potentiometers to i i, inclusive. The junction of each of the Xed resistors 5t to 53, inclusive, with the potentiometers 58 to 'i i, inclusive, are grounded by a common lead 64. The latter also provides ground for all the rectifiers 55 to 5B, inclusive, through its connection to leads 'I2 and 13. The output of rectiiier 59 is applied to the output ends of the resistors of potentiometers 68 to 1|, inclusive, and preferably with a relay winding 55 in series therebetween. Each of the resistors Sii to 53, inclusive, is connected at its ungrounded end to a coil terminal of one of the relays 'I9 to 52, inclusive. The other coil terminal of each of relays 'iii to 82, inclusive, is connected with a tap that is variably adjustable on one of the potentiometers 58 to il, inclusive. The positive terminal of a battery 53 is applied to each of the polar relays .19 to 32, inclusive. The function of relays 'i9 to 82, inclusive, is to make and break contact and to determine the direction of current flow in circuits energizing a plurality oi servomotors 'l5 to lil, inclusive.

Reversible electric servomotors l5, 1B, TI, and 18 are each mechanically connected with one of the missile control members such as rudder, elevator, throttle, etc. of the aircraft or other vehicle which it is desired to control. The mechanical connections with the movement of potentiometers, are shown by dashed lines in Fig. 2, as 269 to 263, inclusive. These connections are also shown in pictorial presentation in Figs. 5 and 6. These servomotors are also arranged to drive the potentiometers t8, 65, lt, and l'i over a stationary contact al, as shown in Fig. 5. The details of this construction are explained below.

These servomotors are electrically connected with loi-directional, polarized center-Cif relays 19, B0, 8|, and 82, respectively, and are connected in parallel with a source of electrical energy, e. g., a battery 83. The negative side of battery 83 is normally connected by reason of the pressure of a spring 55d to a movable contact, open circuited at terminal Y Fig. 2, of relay 65. Lead 84 connects the positive side of the battery 83 with relays '55, Se, and A lead 535 connects the negative side or the lbattery 83 through relay GS with all four servomotors l5 to "i8, inelusive, when the relay winding 65 is energized by the passage of signal through the band pass lter 49. Any suiiicient dierence of potential at the coil terminais of relays 79, 80, 3l and 82 causes the relay armature to close in one direction or the other to move the corresponding control accordingly. The position of the electrical ,null point on each potentiometer atany particular time determines the control setting that will be accomplished.

To effect a change in the position of electrical null point on any of the potentiometers 58, 69, 10, or 1i, in the signal receiving station, hence, to control proportionally the missile or airplane through a servomotor, it is necessary only to adjust one of the variable attenuators i6, I1, i8, or I9, in the signal transmitting station shown in Fig. 1, in order to vary the amplitude of the transmitted signal for the channel involved. If an attenuator in the signal transmitting station is shifted to increase the amplitude of a certain transmitted signal, the servomotor that is controlled, as described, by that signal, will operate in such a direction as to move the contact of the potentiometer in the signal receiving station nearer to the ungrounded side of that potentiometer. Conversely, i1" the attenuator is readjusted to reduce the amplitude of the same transmitted signal, the servomotor will operate in the opposite direction.

In the preferred method, the several signal generators il, i2, i3, and lf3 are adjusted to have equal amplitudes of output voltage, and the modulator 28 is arranged to effect 100 per cent modulation of the radio frequency carrier wave when each attenuator or potentiometer 55 to ll, inclusive, is set for maximum amplitude of transmitted signal. The receiving system of Fig. 2 is so adjusted that the voltage across each potentiometer is at every instant equal to the voltage that would exist simultaneously across any of the load resistors 55, 6l, 52, and 53, ii the corresponding attenuator in Fig. 1 were set for maxlmum amplitude of transmitted signal.

Additional relays such as relay 56, Fig. 2, may be incorporated in one or more of the channels to accomplish other controlling functions of an on-off or stepping type. Furthermore, by employing selectively any one of several standard frequencies for the constant amplitude reference signal, using relays in the relative position of relay 56 to switch the polarized relays to different sets of servomotors and potentiometers for each case, it is possible to shift from one group of controls to another and thus to accomplish settings of many different controls in rapid succession.

Now referring to Fig. 3, this figure shows a transmitter circuit at a control station indicated as 15| in Fig. ll. This station is more elaborate than that of Fig. l and is capable of a greater extent of control. The signal generators it, il, |52, 53, iM, and |55, are like signal generators il to i5, inclusive, in Fig. l, but the arrangement is such that the iirst four signal generators send signals into channels controlled by variable attenuators or potentioineters ldd, HH, |08, and 59, or alternatively, by the variable attenuators or potentiometers ils, lli, li 2, and IIS, or by pulsing switches i122 to H5, inclusive. Signai generators ill and m5 send signals or pulses of constant out differing frequencies through fixed attenuators H5 and H6, respectively, and then through amplifiers ill and H8, respectively, the output from which go through leads i I9, and 25 to the terminals of a threepoint switch i2 l.

As the circuit is shown, the output of the signal generator H35 is being taken by turning switch lZi to contact 2, the output of signal generator 04 may be taken, or by turning the switch further to open-circuited contact 3, no signal from either generator it or 555 taken. Switch I 2| is a rive-deck switch and the resulting contacts of its separate decks are numbered identically.l With switch |2| in the number 1 position, variable potentiometers |96, |91, |88, and |09 are connected. With switch |2| in the number 2 position, variable potentiometers H0, |2, and ||3 are connected. With the switch |2| in the number 3 position, no output from signal generators 04 and |05 is taken, the signals in the rst four channels are controlled by on-of keys or switches |22, |23, |24, and |25. rlhe rst four channels feed signals to ampliers |25, |21, |28, |29. The fifth and sixth channels feed signal to amplifiers ||1 and H8. All six anipliers are connected in parallel to a lead |30. Another lead |3| is connected to amplifiers |25, |21, |28 and |29 in parallel, and to the movable arm of switch |2|. A modulatoll |32 receives its input from the leads |38 and |3|. It transmits them to a radio transmitter |33 having the usual antenna |35 and ground |35. Additional ampliiiers may be interposed between the signal generators and the potentiometers or attenuators if desired.

Referring to Fig. 4, the controlled station indicated as 100 in Fig. l1 has a radio receiver |35 with antenna |31 and ground |38. The audio or super audio signal from radio receiver |38 is conducted through leads |39 and |68 in parallel to a series of frequency-selective filters IM, |42, |53, |44, |45, and |56, which individually pass frequenciescorresponding to one of those originating in signal generators |00, |8|, |52, |03, |89, and in Fig. 3. Signal passed by the individual band pass filters is conducted separately to ampliers |51, |48, |59, and |59, |5| and |52 and then to full wave rectiers |53, |55, |55, |56, |51, and |58, respectively. The resulting signals from the output sides of the iirst four rectiers, which are in the primary control channels of the system, are fed to the load circuits represented by resistors |59, |55, |5|, and |62. On the other hand, outputs from rectiers |51, and |58 pass through solenoid windings |63 and |66, respectively, of relays |65 and |68, and then by means of the lead |61, which is connected to both relay windings, the outputs are conducted to the load circuit composed of eight variable follow-up potentiometers |68 to |15, inclusive. The potentiometers are connected in parallel. Two of the potentiometers are used for each of the four primary control circuits. A ground wire |1827 connects all six rectiiiers |53 to |58, inclusive, to ground |16, and the battery |11 has its positive terminal connected to relay |65, while its negative terminal is connected by leads |18a, and |186 to ground |16. A lead |19 provides an electrical connection between a contact of relay |66 and a contact of relay |55. A lead |80 is con-- nected between each of the resistances |59, |68, |6I, and |62 and the pairs of Variable potentiometers |68 to |15, inclusive, and is connected by lead |186 to ground |16.

` Switching relays |8| to |88, inclusive, are connected in pairs into the four primary control channels mentioned above. These switching relays are energized in groups by battery |11 depending upon the settings of relays |65 and |66, as will be hereinafter more fully explained. The switching relays 22| to 225, inclusive and 24| to 264, inclusive, are ganged in pairs and are normally spring pressed downward.

Insofar as Fig. 4 is concerned, the groups of relays that are energized simultaneously, consist of four each. The groups are distinguished by their being connected to a common contact junction eters |69, |1I, |13, and |15. standard vor reference signal is taken from signal.

marked either X or H. The Contact 220 of relay |65 is also marked X and the contact 236 of relay |66 is also marked H. Relays X are energized through contact 220 (X) and relays H are energized by contact 236 (H). Relay windings X and contact 229 are always in conjunction; likewise, relay windings H and contact 236 are always joined. Switching takes place through the relays |65 and |68, respectively.

It is only due to the complexity of the Fig. 4

diagram that connections between the relays X. and the point X and the relays H and the point H l cannot be shown without making the rest of the diagram unduly complex. The letter Y designates open circuited contacts.

Polarized center-off relays |89, |90, |9|, and |92, one for each primary control channel, are respectively connected by leads |93, |94, |95, and |96, in their respective control channels to the junctions of the particular rectier and the load circuit within that channel. The other input terminals of the polarized relays |89 to |92, inclusive, are connected by leads |91, |98, |99, and 288, respectively, to switching relays |82, |855, |86, and |88. Leads 26| to 208, inclusive, connect all eight switching relays with the movable contacts of the eight variable potentiometers |68 to |15, inclusive. A battery 209, having its negative side grounded, is connected by a lead 2|() to the armatures of polarized relays |89 to |92, inclusive.

When a signal or pulse passes filter |55 and ilows through the channel containing relay |65, it closes relay |65 to the left against contact 220 and applies the positive potential of battery |11 to the junction X and energizes the relay windings 225 to 232, inclusive. The energization of the relay windings 225 to 228, inclusive, causes the relays |8|, |83, |85, and |81 to close toward the left. The energization of the relay windings 229, 238, 23|, and 232 causes the relays 22|, 222, 223, and 226 to close upwardly. The closing of relay |8| toward the left causes a signal to pass from the tap on potentiometer |68 through the relays |8| and |62, which are spring pressed toward the right, to the lower coil terminal on polarized relay |89. In like manner, upon the closing of the other relays |83, |85, and |81 toward the left, the respective channel signals are passed to the lower coil terminals on the polarized relays |98, |9|, and |92. The polarized relays |89 to |92, inclusive, control, by means of battery 209,

the reversible servomotors 2|5, 2|6, 2|1, and 2|8,`

respectively, which are mechanically linked as shown in Fig. 5 to the corresponding potentiometers |58, |18, |12, and |15. Thus, when the standard or reference signal is taken from signal generator |06 (Fig. 3) by closing switch |2| against contact 2, the potentiometers H0, H2 and ||3 control the servomotors 2|5, 2|6, 2li and 2|8, respectively.

Similarly, the switching relays |8| to |88, inclusive, are controlled by relays |65 and |66 so that when a signal exists in the channel containing relay |66, the polarized relays |89, |90, |9|, and |92 are connected to the movable contacts on the respective potentiometers |69, |1|, |13, and |15, which then control the switching relays 231, 238, 239, and 220. The polarized relays |89 to |92, inclusive, control, by means of battery 209, the reversible servomotors 2| I, 2|2, 2|3, and 2M, respectively, which are mechanically linked, as shown in Fig. 5, to the corresponding potentiom- Thus, when the generator (Fig. 3) by turning switch 2| to position 1, the potentiometers |06, |01, |08, and |09 control the servomotors 2| 2|2, 2|3 and 2|4 respectively.

When switch |2| is closed on position 3 (Fig. 3) the keys |22, |23, |24 and |25 may be used to transmit one or more impulses in succession. The control system of Fig. 3 differs from that of Fig. l primarily in the fact that it offers control of a greater number of functions. The system of Fig. 1 incorporates a single standard signal and four separate controlling signals that are adjustable in amplitude at the discretion of a pilot or operator and therefore, the system is adaptable to the continuous proportional control of four separate functions. The transmitting system of Fig. 3 employs four similar controlling signals, but it has two separate standard signals either one or neither of which may be transmitted, depending upon the setting of transfer switch |2I. When that switch is in position 1, the standard signal from the signal generator |05 is fed to the modulator |32 and is then transmitted by the radio transmitter |33. When the switch |2| is in its position l, the controlling potentiometers |00, |01, |90, and |09 are in the circuits of signal generators |50, |0|, |02, and |03, respectively. When switch |2| is in its position 2, the standard signal from signal generator |04 is substituted for that from signal generator |05, and also the controlling potentiometers ||0, |2, and ||3 are substituted for those previously mentioned in the respective circuits of signal generators |30, |0|, |02 and |03. Finally, when switch |2| is in its position 3, neither one of the two available standard signals is transmitted and none of the controlling potentiometers is in circuit. Instead, the switches |22, |23, |24, and |25 provide on-oif control of transmission of the respective controlling signals from signal generators |00, |0|, |82 and |03. When switch |2| is in position 3, there is no modulation signal transmitted from the system unless and until one or more of the switches |22, |23, |24 and |25 are closed by the operator.

The remotely controlled system of Fig. 4, indicated as 108 in Fig. 11, is intended for use in conjunction with the transmitting system indicated as 122 in Fig. l1 and shown in Fig. 3. In Fig. 4, the filters |4I, |42, |43, and |44 are adjusted to pass the four principal controlling frequencies that are generated at the transmitting system. The filters |45 and |46 are adjusted to pass the two separate standard signals, either one, but not both of which may be received at any given time depending upon the setting of a certain switch at the transmitting station. There are three separate conditions of operation to be considered, as follows:

a. Standard signal is being received on the frequency of filter |45, but no signal is being received on the frequencyof filter |45;

b. Standard signal is being received on the frequency of lter |45, but no signal is being received on the frequency of filter |45;

c. No signal is being received on either the frequency of filter |45 or the frequency of filter |46.

In the case (c) above, the signal passing through filter |45, after amplification and rectification, passes as direct current through the actuating coil |53 of relay |65 and thence through the follow-up` potentiometers |14 and |15, which are connected in parallel to the return or ground circuit. This rectied signal current causes the and 224 to solenoid 254.

relay |65 to close to the left, thus connecting battery |11 to the inner relay contact 220. Contact 220 is connected to the actuating coils 225, 225, 221, 228, 229, 230, 23|, and 232 of each of the relays |8|, |83, |85, |81, 22|, 222, 223, and 224, all of which are switching relays that serve to determine which of the servoinotors or actuating devices will be controlled under this operating condition.

Description of the controlling operation will be limited to the control function represented by the signal frequency of filter |44 which will be seen to communicate with the polarized center-off relays |||2 and the servomotor 2|4 or 2li! or the solenoid 254. With relay |65 closed to the left in a manner just stated, the switching relay |81 also closes to the left and thus connects the polarized relay |02 to follow-up potentiometer |14. Also, the closing of relays |$5 to the left, causes the switching reiay 224 to close upwardly and thus connects the output terminals of relay |92 to the reversible servornotor ZES. Thus, the follow-up potentiometer |14 and the servomotor 2m, which are mechanically linked together, are controlled by the signal passing the filter |44 when the standard signal through filter |45 is being used. For the condition of standard signal at lter |45 and no signal at filter |45, described above in (b), there is no signal on the frequency of lter |45 and therefore the relay |55 and all vother switching relays controlled by it are open.

However, if there is a standard signal received on the frequency of lter |45, and that signal closes switching relay Hit, the terminal H of relay contact 235 is connected with the battery |11. When the relay |65 is closed toward the right by spring pressure and when signal is passed through filter |46 to energize relay winding |54, relay |66 is closed toward the left. The positive potential of battery |11 is then applied to the I-I terminal of contact 235. The contact H is common to contact 236 and to the relay windings 233, 234, 235, 24|, 242, 243, 244, and 245, all of which are therefore energized from the positive potential of battery |11. All contacts Y are open.

The closing of relay |88 connects the energizing coil of the polarized center-off relay |92 to the follow-up potentiometer |15, and closing of the switching relay 240 connects the output contacts of the same relay |92 to the reversible servomotor 2|4. Thus, the follow-up potentiometer |15 and the servomotor 2|4, which are mechanically connected together, are controlled by the signal on the frequency of filter |44 when the standard signal through filter |43 is being used. It will therefore be apparent that upon the simultaneous reception of signals passing filters |44 and |46, the servomotor 2| 4 may be caused to perform mechanical work such as the adjustment of a control upon the missile or the like.

Under the conditions described above in subparagraph (c), there is no signal on either the frequency of lter |45 or that of filter |45, and therefore the switching relays resume their spring-pressed positions with the relays m5 and |65 open circuited. It will be noted that in this case, the polarized, center-off relay |92 is connected across the load resistor |02 and ground and is not associated with either of the followup potentiometers |14 or |15. Also, the uppermost one of the three output contacts of relay |82 is connected through switching relays 240 Under this condition, the relay |02 remains open at all times when no signal is being received on the frequency of i'llter potentiometers |14.

ll |44, and the solenoid 254 is thus deenergized. However, when a signal is received on the frequency of the filter |44, the potential difference that is developed across the resistor |52 serves to close relay |92 in the up direction, thus connecting battery 299 to the solenoid 254.

In this particular condition of operation, there is no proportional control feature'involved because the solenoid is either energized or deenergized, with no intermediate conditions or positions provided. The solenoid 254 may be used to operate any leveror other two-position device such as a stepping switch, valve, or other mechanism.

Battery 299 energizes either the servomotors or the solenoids depending upon the position of relay 244 and the position of relay 224 and |92. The -ow of energy to these relays is controlled through filters |45 and |49. When the armature of relay |92 is energized, the relay 244 or 249 is connected to relay |92 either one way or the other. The positive terminal of battery 209 is closed upwardly and the contacts X and H are deenergized. Then battery 299 can energize solenoid 254. When contacts X and H yare deenergized, relay |92 cannot close downwardly. The lower coil terminal of relay |92 is grounded through the deenergized relays |81 and |88 since the polarity of the voltage applied to the upper coil terminal cannot be reversed because of the fixed manner of connection of the rectiiier |59. The upper coil terminal is connected with the positive terminal of load resistor |62. Relays |89 to |92 act as one-way relays when terminals X and H are both deener- .l gized. For example, when X is energized and H is not energized, the lower coil terminal of relay 92 is connected to the movable contact of the The armature of relay |92 can now close in either direction. If it closes upwardly, the positive terminal of battery 299 is connected through upper armature of relay 244 to the upper armature 224 of relay 232 and thence to the upper power input terminal of motor 2|8. When relay |92 closes downwardly, the positive terminal of battery 209 is connected through the lower armature of relay 244 to the lower armature of relay 232 thence to the lower power input terminal of motor 2|8. When terminal H is energized and terminal X is not energized, the relay |92 acts as a polarized, centeroi relay because its lower coil terminal is con-j nected to the movable contact of potentiometer connected through the upper armature of relay 244 and thence to the upper power input terminal v of motor 2|4. When relay |92 is closed downwardly, the positive terminal of battery 299 is connected through the lower armature of relay 244 to the lower power input terminal of motor '2|4. Terminals X and H cannot be simultaneously energized, because the standard signals on the frequencies of filters |45 and |46 are never transmitted simultaneously. See switch |2| on the transmitter (Fig. 6).

It is to be understood that the servomotors are all provided with split field windings (not shown) so that energization of one terminal will produce the opposite direction of rotation from that produced by energization of the other terminal.

In Fig. 4, due to the complexity of the diagram, it is impossible to show the mechanical linkages which exist between the servomotors and the potentiometers without making the remainder of l2 the diagram unduly complex. Such linkages connect servomotors 2||, 2|5, 2|6, 2|2, 2|1, 2|3, 2|8, and 2|4 with potentiometers |98, |99, |19, |1|, |12, |13, |14, and |15, respectively.

Referring now to Figs. 5 and 6, the nature of the mechanical linkage between a reversible servomotor and a potentiometer is illustrated. A servomotor 15 is bolted to a gear box 94, which contains a driving pinion 95, which is in mesh with a larger gear a, mounted on a countershaft 91. A smaller gear 9B on countershaft 91, drives a larger gear 99a on a second countershaft 91a which projects from the forward end of the gear box 94. On the projection is mounted a groove pulley or reel 99 and its associated cable 99a. Just within the case is mounted the potentiometer 68 which is essentially a resistance coil mounted on a circular insulator and making contact with a spring-pressed brush 99 in a stationary brush holder mounted in thhe floor of the box 94. The potentiometer 68 is driven by the countershaft 91a.

In this arrangement, the total angular movement of the coil of the potentiometer 63 is equal to the total angular movement of the control cable reel 99. An arrangement in which the potentiometer would be stationary and the contacts movable .would be the full equivalent of the above combination.

The remote control system represented by the transmitting system of Fig. 3 and the receiving system of Fig. 4 provides an additional group of four proportional controls for setting the trim tabs, cowl flaps or other auxiliary devices on the missile, test airplane or the like. These controls must be accurately positioned, but do not require continuous attention or adjustment by the remote pilot. This particular embodiment of the invention, which also includes the on-oi switches or keys |22, |23, |24, and |25 which operate the solenoids 25|, 252, 253, and 254 on the controlled missile. These on-ofi or step function controls are provided for the operation of landing-gear retraction and extension, dive-brake opening and closing, the turning on and oi of cameras or other special devices on the missile or airplane, and for any other functions that have only two positions or conditions of operation.

In the preferred manner of application, one of the solenoids on the missile is used to actuate a chain of lock-in relays or a stepping switch of the type commonly employed in automatic telephone exchanges; another solenoid is used to reset the relay chain or stepping switch to the home position; a third solenoid is used to energize the particular step function selected in the positive direction and the remaining solenoid is used to operate the selected step function in the negative direction. To illustrate the manner of use of this feature of the total control system, let it be supposed that on a particular installation, the landing-gear retracting mechanism is connected to the third position of the relay chain or steppingswitch. To actuate the landing gear retracting mechanism, the remote pilot will close and open three times the stepping switch that controls the first solenoid on the missile or aircraft and will thereby advance the relay chain or stepping switch to its third position. If he then desires to retract the landing gear, he will close the actuating switch that controls the third solenoid on the missile or airplane. Such closing will cause positive direction of operation of the selected step function.

On the other hand, if he desires to lower the 13 land-ing gear, he 'will close the actua-ting switch for the fourth solenoid. Such closing will accomplish negative direction of operation of the selected step-function. After completion of the desired operation, the remote pilot will close his second step-function switch, thereby energizing the second solenoid on the airpl-ane and returning the relay chain or stepping switch to its home position. A step function system of the type just described, incorporating four on-of switches or two double-throw switches at the remote control transmitting station and four cooperating solenoids on the remotely controlled airplane may be 4used to control as many separate step functions as desired. The number of such functions available for control is limited only by the number of discrete steps in the relay chain or the stepping switch on the test airplane.

It will be seen that the transmitting system of Fig. 3 is capable of controlling selectively two separate groups of four each proportional controls and one set of four each on-oi or stepping controls. There are two different ways in which the transfer switch I2! can be utilized which are as follows:

a. It can be manually set by the controlling pilot, who would thus select the particular group or" functions desired to be controlled at any time, or;

b. The form shown. in Fig. 3c can be continuu ously and automatically driven through its several positions by a motor or other continuously acting device, thus to provide automatic sampling of each of the separate control groups at regular intervals.

With rapid action of the switch I2, the system can be made to display for all particular purposes,

continuous availability of all twelve of the separate control operations. The switch may be mechanically actuated in the manner just mentioned or it may consist as an equivalent of a wholly electronic device in which electronic gates are opened and closed in predetermined sequence by a controlling oscillator or pulse generator.

Referring now to Fig. 3a, the switch it! may comprise in each one of its decks a plate-like circuit 52 Ib which is made from an insulating material such as a plate of synthetic resin. Mounted centrally therein for rotation is a shaft I'la which may be driven by a separate electric motor. not shown. Attached to the shaft 12m is rotat- -ing arm IZIc which bears at its outer end a ksmall. wheel l'? lg. The wheel I2 Ig is arranged to make contact with at least three open segments I2Id, IEIe and IE! f, respectively, that are vertically mounted upon the base plate Illib. Lead |213 connects with segment IZId; lead I3i connects with the shaft end of the movable arm I 2 lc and lead Il@ connects with the segment Isla. The segment i12! f an open contact. Rotation of the arm illlc, therefore makes successive contacts with the segments after the manner of the commutator or distributor of an automobile engine.

The circuit diagram of Fig. 7 shows a fourchannel radio control transmitting system of the same type as that shown in Fig. 1 and as EZ in Fig. ll, but with two important additions:

which the pilot or operator can determine at any time the control position that is being called for by the transmitting system in each of its separate channels.

As in the other transmitting systems previously described the present arrangement employs five signal generators II', ill', I3', and l5 which are identified in Fig. l as II, I2, I3, It, and I5. Each of these signal generators produces a constant i'requency and constant amplitude of output, but no two of the frequencies are the same. The signal generators II to I4', inclusive, as in the previous showings, apply their outputs to variable potentiometers I5 to I9', inclusive. The signal generator I5 which delivers its output to a constant load resistor tile, produces the standard or reference signal for the system shown in Fig. 7. rl`his signal passes through the amplifier and filter combination .l'l, thence into the modulator 28', the radio transmitter SI', and is radiated from the antenna e2. The signal generator I4', which produces another signal, delivers its output to the network consisting of potentiometer i9', resistor 3G! and potentiometer S232. The potentiometer is the control element by means of which an operator can obtain at the frequency of generator It', a signal having an amplitude from zero to the full output of the signal generator. The potentiometer i9' in conjunction with the resistor constitutes the trim adjustment which will be explained later. The output signal from potentiometer 3M passes to a nlter and amplifier unit 23 and thence to the same modulator 2li', transmitter SI and antenna 32.

The other channels following signal generators II', I2' and I3 are similar to that of Id except in the matter of frequency. They operate in the same manner to produce control signals that can be separated and individually used at the receiving station. The control position indicators 36d, 3:'35, and 3% are zero center, directcurrent instruments observable by the pilot at the remote control transmitting station. These instruments are employed in differential vacuum tube voltmeter circuits to measure the relationships between the standard signal amplitude and the adjusted amplitudes of each of the other control signals.

The action of the trim-adjustment potentiometer will be explained with reference to the channel of signal generator lll. The resistance element of the trim-adjustment potentiometer I9 connected in parallel with the control potentiometer 3F32. One end of the range resistor Sill is connected to a center tap on the potentiometer and the other end of this resistor is connected to the movable contact on potentiometer i9. To examine the operation of this trim-conltrol adjustment, the case in which the movable contact on potentiometer I9 is in the center of that potentiometer, will be rst considered. In such case, both ends of the resistor 3S! are always at a potential midway between ground and the output potential of the signal generator I d. Hence, there is no potential difference across resistor Sill and no current flows through it. Under this condition, the presence of potentiometer I9 resistor has no effect on the control pon tentiometer 332 and the latter potentiometer maintains linear relationship between geometrical setting and output voltage.

However, if the movable contact on potentiometer I9 is moved to the top position possible in Fig. '7, it will be noted that the resistor SGI is in shunt with the upper half of potentiometer 382.

. potentiometer.

/ coming grid signal.

'In this condition, the geometrical center of potentiometer 362 is at an electrical potential greater than one half of the total potential output of the signal generator la. This maximum setting of potentiometer I9 produces therefore, an electrical center point on potentiometer 302 that is somewhat below the geometrical center of that On the other hand, if the movablecontact on potentiometer i9 is placed at the vlower end of that potentiometer, then the resistor 3E!! is in shunt with the lower half oi the vcontrol potentiometer and thus moves the electrical center of potentiometer EQ2 above its geometrical center.

When the movable Contact on the potentiometer I9" is at any other position than its center or Vupper or lower limits, the elect is to place un- Thus, the combination of potentiometer is and resistor 3d! provides for unsymmetrical shunting of the two halves of potentiometer 3M, in either sense about the symmetrical condition and thereby furnishes a trim control for the flight control element on the controlled airplane or missile that is actuated by the channel originating in signal generator Ill'.

Four separate control position indicator circuits are shown in the lower part of the diagram of Fig. 7. Since all of these indicator circuits are substantially identical, the numerals designating the parts of the other three indicator circuits are the same as those of the first except that they are followed by the letters a, b, and c, respectively.

The following explanation will therefore be ap. plied only to the first circuit at the left of Fig. '7.

That circuit comprises the indicating meter 303, the vacuum tubes 324 and 325, and associated circuit elements. These vacuum tubes are used in a dierential cathode-follower arrangement with;

each tube initially vbiased to plate current cut-olf so as to produce half-wave rectication of the in- This eifect is accomplished by inserting in the cathode circuits comparatively high resistances 326 and 321 to produce essen-lf3 tially full cathode-follower action in the vacuum tubes 324 and 325 and, by initial adjustment of the potentials of the batteries 308 and 309 to produce plate current cut-olf in the respective vacuum tubes. The indicating meter 3M is connected across the shunt resistors 3l@ and 3H, each of which is in the cathode circuit of one of the vacuum tubes. The filter condensers 3 l 2 and 3I3 may be connected across the shunting resistors as shown, to smooth pulsations of meter current that otherwise would be caused by the halfwave action of the plate currents in the vacuum tubes. It will be noted that signal Voltage from the standard frequency generator l is fed through a blocking condenser 3M to the potentiometer SI5 which is in the grid circuit of the vacuum tube 3134. Similarly, the adjusted output Voltage of potentiometer 352, which is in the control circuit of the signal generator lil', is fed that the potentiometer 3532 is irst placed at the lower limit of its travel, thus delivering zero signal at the frequency of signal generator I4. Then, as the signal generator l5 has been adjusted to Y its normal voltage output. the potentiometer 3l5 is adjusted to a point which gives sufficient grid signal to tube 324 to produce full-scale deection of the meter 303. Next, the control potentiometer 3M is moved to its top position, thus delivering maximum signal output at the frequency of signal generator ld. The potentiometer 3H is adjusted to such a point that the indicating meter shows full-scale deliection in the direction opposite to that produced above. After adjustments have been made in this manner, the indicating meter 303 will show deflections which are at all times indicative of the electrical position of the control potentiometer 302. For example, when the potentiometer 362 is set to its electrical center position, the meter 393 will stand at its zero center, thus indicating that the control channel represented by the signal generator lll is set to produce neutral or center position of the rudder or other controlled element at a remotely-situated receiving station. The main channels as represented by meters 303, 3%, 305, and 3936 therefore furnish a complete presentation to the pilot of the position settings being called for by the transmitter station for the flight controls of the missile or airplane.

The schematic diagram of Fig. 8 shows a complete radio-controlled receiving station of the general type that has been previously described, but incorporating certain additions and modifications not before illustrated. For simplicity, the diagram shown on Fig. 8 includes only two channels for control. It is to be understood that four or more signal channels, besides the standard or reference channel, generally are to be used. Among the more important new features indicated on this diagram are the following:

a. The follow-up potentiometers Mil and 402 substantially correspond to the follow-up potentiometers 68 to 1l, inclusive, in Fig. 2, but 401 and e132 are connected in alternating current circuits ahead of the rectiers 4H to 414, inclusive, in Fig. 8, rather than in the direct current circuits following the rectiers 55 to 59, inclusive, as are potentiometers 68 to 'l l, inclusive in Fig. 2;

b. Thermionic full-wave rectication is used instead of the dry-disc type shown in Figs. 2, 4, and 10;

c. Gas-filled electronic tubes are used as sensitive relay devices;

d. A hydraulic servo system is shown in place of the electric motor servos indicated in the preceding iigures;

e. An anticipating or anti-hunting circuit is included;

f. The system includes a throw-out switch by which a human pilot or operator can quickly throw the complete remote control system into or f out of operation; and

g. Signal lamps are provided to indicate to a human. check pilot when the transmitter station is calling for control settings different from those existing on the controlled airplane or missile.

Major subdivisions of the control-receiving system of Fig. 8 will be mentioned briefly and will be followed by detailed description of one of the two channels shown. The other channel operates in a similar manner.

The antenna lili receives a modulated radio wave from any one of the transmitting stations shown in the drawings. The receiver 4l' demodulates the radio wave and delivers the combined modulation frequencies to the inputs of therthree lters 45', 4S', and lll', which are connected in parallel. These lters are of the bandpass type and are individually adjusted to pass the frequencies corresponding to outputs of signal generators I3', I 4', and l5 at the transmitting station (Fig. 7). The output of filter 41, which is the standard or reference signal, is applied across the two follow-up potentiometers 401 and 402 which are in parallel. The output of the follow-up potentiometer 402 is applied through an amplifier 403 to the primary winding of the transformer 404 and the output of the other follow-up potentiometer 401 is similarly connected to its transformer 405 through amplifier 406.

The output of the filter 46 is connected directly through the amplifier 407 to the primary winding of the transformer 408 and the output of the filter 45 is similarly applied through amplifier 409 to the primary winding of its transformer 410. The secondary winding of each of the transformers 410, 405, 408, and 404 is connected to a vacuum tube 411, 412, 413, or 414, respectively, in a conventional full-wave rectification circuit that includes a fixed load resistor 415, 416, 41'1, or 418. These rectification circuits are grouped in pairs, one variable-amplitude control channel being paired with one reference channel, and the two load resistors of each pair (for example 415, and 416) are connected in polarity opposition across a resistive network 419, 420 having its midpoint grounded. Gas-filled electronic tubes 42E, 422, 423, and 424 have their control grids connected to the resistive network on opposite sides of its neutral or ground point, and these tubes are thus differentially controlled by the rectified signals. In the plate circuit of each of the gasfilled electronic tubes is a relay winding 425, 426, 412i, and 428 which closes a corresponding relay switch 483', 480, 128i', and 481, respectively, when the associated one of the above tubes is rendered conducting by an increment of positive signal applied to its grid. One contact Y of each of these relays 480, 460', 481 and 481', is an open contact. Each of the relays 430' or 481', when closed downwardly and relays 488 and 418i, when closed upwardly, energizes a vlinding and thus opens one or more solenoid-operated hydraulic valves 423 to 438, inclusive, which control the motion of hydraulic servos 439, 443. Finally, each one of the hydraulic servos 435 and 440 is connected by some suitable mechanical linkage such as a flexible cable and pulley arrangement (not shown) tc the rudder (not shown) or to some other controlled element on the missile or airplane.

For a more detailed analysis of the operation of this remote control system, the channel represented by filter 46 leading to the hydraulic servo 439 will be considered. The other control channel through the filter 45 and leading to the servo 440 is substantially a duplication of the channel through the filter 46.

Before the system is placed in operation, a source of alternating current power is connected to the A. C. terminals on transformers 441, 442, 443, and 444. Next, cathode bias for the gasiilled electronic tubes 421, 422, 423, and 424 is separately adjusted by the potentiometers 445, 446, so that each tube is nonconducting and the relays 480', 480, 481 and 481 are therefore open when no controlling signals are being received through the filters 4T', 45' and 45. Positive bias applied to each such cathode should be only slightly greater than that required to render the tube nonconducting, so that tube conductivity can be achieved by application of a small increment of positive grid signal. After this initial adjustment has been made, the system 18 is ready for operation and the receiver may be switched on.

The standard signal is received through the filter 4l at a fixed and constant amplitude, and the controlling signal is received through its filter 46 at an amplitude which may be varied at the transmitting station by the potentiometer 382 of `Fig. 7. Let it be assumed that the amplitude of the controlling signal through 45 is set at maximum and is equal to the total amplitude of signal through the reference channel 4'1. Let it also be assumed that the controlling potentiometer 302 on Fig. 7 is set at its midpoint. The incoming signal through amplifier 4l is rectified by the tube 413 and is thus converted into a D. C. potential across the load resistor 416 with the polarity as shown. Similarly, the other signal through amplifier 433 is rectified by the tube 414 and appears as a direct potential across the load resistor 415. In this case, the voltage across resistor 416 is twice that across resistor M5 because of the assumed setting of the potentiometer 302.

Since the resistors 415 and 416 are effectively connected in parallel, a current will iiow through the resistive network 419 comprising resistors 449, 450, 451, and 452, and the direction of this current flow will be such as to make the top of resistor 452 positive with respect to ground and the bottom of resistor 450 negative with respect to ground. The resistor 451 and condenser serve as a filter to produce essentially pure D. C. through the resistor 452 and the resistor 449 with condenser 454 serves the same purpose with respect to resistor 450. The negative potential at the bottom of resistor 453 is applied through the resistor 463 to the control grid of tube 42| and thus provides additional bias on this tube in the direction of nonconductance. On the other hand, the positive potential at the top of the resistor 452 is applied through resistor 455 to the control grid of tube 422 and produces an effect opposite to that of the initially-applied positive cathode bias and serves to render tube 422 conductive when positive half-cycles of plate voltage are applied through the transformer 442.

The resistor 455 is introduced into the grid circuit of tube 422 to limit grid current to a negligible value during conducting half-cycles in that tube. Rendering the tube 422 conductive results in the closing upwardly of relay 480 which thereby energizes and opens solenoid-operated valves 429 and 432. A resistor 456 in the plate circuit of tube 422 serves to limit maximum plate current through that tube to a safe value. Opening of the valve 429 admits hydraulic iiuid to the bottom of the servo. 433, and the simultaneous opening of valve 432 connects the top of the same servo to the hydraulic reservoir. This sequence of events causes the servo 438 to move the servo piston rod 45'1 in a direction to produce a desired result such as down motion of a control element on the missile or airplane` The foregoing description shows how the servo is caused to move and the direction of that motion. The next matter to be considered is how far the servo will move and under what conditions it will assume a xed position. The follow-up potentiometer 482 is mechanically connected to the movable piston shaft of the servo `439 as indicated by a dashed line 482 in such a manner that these two elements move together and have coincident limits of travel. The mechanical linkages 482 and 483 connect the hydraulic pistons 451 and 484, With their follow-up potentiometers 462 and asienta Mil, respectively. Recalling that'aservo'motion Was initially produced because the signal through ampliiier 40TH was greater than that through amplifier 423, it will be seenthat movement of the potentiometer 482 toward its upper limit will increase the signal through ampliiier 403 and thus tend to establish equality of the voltages developed across load resistors 4 l 5 and 4 l 6.

Since the signals through ltersv46' and 4l' were assumed to. be equal, it isapparent that the signal through amplier 403 will be equal to that through amplifier 40? when the potentiometer 402 is at its extreme upper position. -Flacement of potentiometer 452 in its extreme upper position produces equality of voltage across resistors H5 and 4|6, reduces to zero the current through resistors 455 and 452 and thus removes all grid signals from the gas-filled electronic tubes 42! and 422. When this condition is reached, relay 434 remainsopen, relay 48) opens, thus closing solenoid-operated valves 429, and 432, and the servo 439 is stopped and hydraulicallyiloclsed in position. Therefore, proper mechanical linkage between the sen-vo 439 and the follow-up potentiometer 452 is that in which the maximum down position of the control elementv on the airplane corresponds to the maximum up position of the potentiometer 402. Similarly, the maximum up position of the control element on the airplane should correspond to the maximum down position of the potentiometer 402. With the iollow-up potentiometer connected in this manner, servo motion always moves the follow-up potentiometer in a direction tending to establish equality oi' signals through amplifiers 453 and 4M. Servo motion stops when that equality is established. The system automatically adjusts a follow-up potentiometer 442 to pick off a definite -fraction of the standard signal through filter 4l" and that fraction is equal to the amplitude ratio of signals sent through the amplifier elements 23' and 2 of the transmitting system 'in Fig. 7.

To illustrate the opposite directionof servo motion, it is convenient to consider the condition in which the controlled element on the airplane is in its full down position and the follow-up potentiometer 482 is in its full up position. If the controls at the transmitting station are then manipulated in such a manner that the amplitude of signal through filter 45 of Fig. 8 is reduced to one half or its former (maximum) value, the voltage developed across resistor 4I5 will be twice that developed across resistor 415. The bottom of resistor 453 Will be positive with respect to ground and the top of resistor 452 will be negative with respect to ground. This situation causes the tube 421 to become conducting, closes the relay 485 downwardly, opens the solenoid-operated valves 435, 43 l, introduces hydraulicV pressure into the upper end of the servo 439, connects the lower end of the servo to the hydraulic reservoir and thus causes the controlled element on the airpiane to move upward from its full down position. It is evident that equality oi signals through ampliers 483 and 4G? will be established, hence, servo motion will be stopped when the follow-up potentiometer 422 reaches its midpoint because it will then be picking oI' 50 per cent of the standard signal through lter 41. Therefore, the controlled element on the airplane will come to rest in its center or neutral position. The dashed lines 482 and 483 which :bear the legend, mechanical linkage indicate a drive for the potentiometers similar to that illustrated and 'described in relation to Figs. 5 and 6.

rn 'regard to the biasing ,system 'emplbyed for the' gas-lled electronic tubes 42! and 422,l particularly with reference tothe anticipating or anti-hunting circuit referred to previously as modiiication (e) contained in Fig. 8, the operation is as follows: Bias voltage is supplied by the battery 472 through the voltage-dividing circuits consisting of resistor 459, resistor 460, potentiometer 445 and resistor 454 for tube 22. The vcircuit just mentioned is used to provide constant but adjustable cathode bias to these tubes. It Awill be noted that the resistor 459 is common to both of the cathode biasing circuits and is also connected through resistors 465 and 456 to the relay contacts adjacent the relay windings 425 and 426, respectively. When either relay winding 425 or 426 is energized, the positive terminal of battery 458 is connected through resistors 465 or 466 to the resistor 459 at its junction with resistors y462, and 464. The closure oi relays 480 or 48B produces from battery A458 an increment ci current inaddition to that from battery 412 through resistor 459 because the battery 458 and resistor 459 have a common ground connection at their negative ends, and thereby apply an additional increment of positive bias to the cathodes of both tubes 42| and 422. rThe eiect oi this action is to bias both of these tubes 42| and 422 farther in the direction of nonconductance, thus requiring a greater amount of positive grid signal to maintain relay closure. It must be understood that after a relay has closed and a servomotor has started lto move its follow-up potentiometer, there is a small but unavoidable delay between the attainment of equal signals in ampliers 403 and 497 and the actual stoppage of servo motion. This delay is due to time constants ofthe various parts or the electrical circuit, to the time required for relay opening, to the time required for the solenoid-operated valves to close and perhaps to other factors.

The practical result is that if no anticipating circuit were provided, the follow-up potentiometer 402 would be driven past its proper balance point before the balance condition could exert its effects to stop the'servo. Such over-shooting could produce errors in the final resting point of the controlled element on the airplane, and, if serious, would result in continuous oscillation of the controlled element. With the anticipating or anti-hunting circuit in operation, however, the cathode bias and grid bias conditions on the gasiilled electronic tube necessary for relay opening are established before the follow-up potentiometer 4t2 has reached its electrical balance position. Values of resistors 45S, 455, and 456 can be chose-n so that, with a given voltage oi the battery 458, a proper amount oi anticipation will be obtained for any given speed of servo movement. In any given installation, servo operating speed does not ordinarily change after having been initially set to a suitable value. rlhe polarity of the increment of cathode bias applied by this anticipating circuit is the same regardless of the direction of servo motion.

A switch 461 which is an eight-pole, doublethrow switch, the arms of which are ganged as shown by the dashed line 485, is provided as an illustration of the modication (j) included in Fig. 8. By the use of the switch 461, the entire remote control system may be thrown in or out of operation at the discretion of a human pilot in the remotely controllable airplane. When the switch is closed downwardly as shown in Fig. 8, the remote control system is fully engaged and operable as described above. However, when this switch is closed upwardly, the servo-actuating valves 420, 430, 34|, and 432 are disconnected from their ground-return circuit to the battery 458 and therefore cannot be operated by closure oi their associated relays 480', 480, 48| and 48|. Also, closing of the switch 461 upwardly energizes and thereby opens the solenoid-operated valve 433 which serves to by-pass and hence to unlock hydraulically the servo 439. The closing upwardly of switch 461 renders the remotecontrol system ineffective and at the same time frees the hydraulic servo system so that the controls on the airplane can be manually operated by a human pilot in the conventional manner.

Signal lamps 468, 469, 410, and 41| are provided, two in each channel of the remote control system to indicate to a human check pilot in the remotely controllable airplane when the remote control system produces relay closure of any of the relays 480 or 48|' upwardly or 480 or 48|' downwardly and thereby calls for servo motion. The signal lamp 410 is energized by the closure downwardly of relay 480 and hence shows when the remote-control system is calling for up motion of a control element on the airplane. Similarly, the signal lamp 41|, which is energized by the closure of relay 480, shows when the remote control system is calling for down motion i the same control element on the airplane. When the system is operating properly, it is impossible for both signal lamps oi any given pair to be turned on at the same time. In a similar manner, a closing upwardly of relay 48| applies the potential of battery 4158 across the lament oi lamp 468 and when the relay 48|' is closed downwardly, the potential of battery 453 is applied across the lament of lamp 469.

The chief practical use of the signal lamp system is to indicate to a human check pilot in the control plane when he may safe-ly switch over from manual to remote control. For example, if an airplane has been taken aloft by conventional manual control and if it is then desired to switch over to remote control from a groundbased or airborne transmitter station, it is desirable that the controlling potentiometers at the transmitting station be set in positions corresponding to the actual positions of the controlled elements on the airplane before the changeover is made. If this condition were not satisfied, more or less violent reactions of the airplane would result when the airplane controls adjusted themselves to the settings dened by the transmitting station. Therefore, the normal procedure is for the human check pilot on the controlled airplane to instruct the pilot at the control station through radio communication to readjust his transmitting controls so that al1 signal lamps on the controlled airplane are 011, indicating that all controls are set as required by the transmitter station. When that condition is attained, it signifies that the remote control system is not calling for any change of servo position on the controlled airplane and therefore, no immediate change of airplane attitude will result from a switch-over from manual to full remote control. The various signal lamps used are preferably or distinctive colors and are so-placed and identified that the check pilot on the controlled airplane can tell at a glance which controls are being energized by the remote control system and the direction of motion that is being called for in each case. All signal lamps are fully oper- 22 ative regardless of the position of the switch 461.

Fig. 9 is a diagram of a remote control transmitting system that is similar to Fig. 1 except for the means by which the combined controlling signals are radiated into space. The relationship between Figs. 1 and 9 is indicated by corresponding numerals with the letter d added. In Fig. 1, the several controlling signals were combined and then were radiated as modulation on a radio frequency carrier wave, whereas in Fig. 9 the combined controlling signals are amplied and then applied to a generator oi light, such as a gaseous glow-discharge tube 500, and are then transmitted through an optical system 50| as modulation on a light beam 502. In the system of Fig. 9, the several signal generators, controlling potentiometers, and isolating amplifiers, and the combined modulation ampliiier 503 operate in substantially the same manne-11 described in connection with Fig. 1.

The combined signals at the output of the amplier 503 are fed through the blocking condenser 504 to the control grid of the vacuum tube 506. The cathode resistor 561 in the circuit of the vacuum tube 506 is provided in the usual manner to generate appropriate cathode bias for operation of that vacuum tube on the linear portion of its characteristic curve, and the by-pass condenser 503 is connected across resistor 501 to provide a low-impedance path for the dynamic components of cathode current. The resistor 509 is connected in the conventional manner to provide a direct current return circuit from the control grid to ground. fr battery 5|6 provides, through the tube 500, cathode-toplate potential dierence for the vacuum tube 506 in the usual manner. r"he gaseous glow-discharge tube 500, which may be a neon tube, is inserted in the plate circuit of the vacuum tube 506 in a manner such that the plate current flows through the discharge tube 56d and thus generates light rays whenever the vacuum tube 5-05 is conducting. The gaseous glow-discharge tube 500 should 'ce one in which the intensity of the generated light is proportional to the electric current passing through that tube.

To illustrate the operation oi' this transmitting system', let it ce assumed rst that the cathode hea-ter (not shown) of the vacuum tube 5% is fully energized, and that no grid signal is being impressed through the condenser 531i. in this condition, the value of resistor 5|?? should be adjusted so that the grid bias with respect to cathode is midway between zero and the maximum negative value for linear variation with plate current. Under this condition, the plate current on Vacuum tube 506 will be set at its normal value, and the intensity of light emitted by the gaseousglow-discharge tub-e 551] will be midway between its maximum and minimum values. Now, if the signal generators, ampliers, and all other parts of the circuit arel placed in operation, a composite alternating voltage war-e containing, in general, ve different frequency components originating in the five separate signal generators, will be transmitted through the condenser 554 to the control grid of the vacuum tube Due to the well known plate--current--versus-grid-voltage characteristics of a vacuum tube such as 505, the current through the gaseous-glow-discharge tube will vary in accordance with the instantaneous values of signal voltage applied to the control grid and will thus produce changes of intensity of light radiated from the discharge tube 5001 Positive increments of signal `voltage applied to the control grid or vacuum tube F36 Will cause increases of the plate current andfhence, increases of light intensity from the gaseousglow-discharge tube 500. Similarly, negative increments of signal voltage applied to the control grid of vacuum tube 506 will decrease the intensity of light from the glow-discharge tube 5M.

Under the stated conditions in which plate current in the vacuum tube 596 is a linear function of applied grid voltage and in which intensity of radiated light from the gaseous-glow-discharge tube E130 is a linear function of the current conducted through that tube, the radiated light intensity will be a time function corresponding to the composite voltage signal wave applied to the control grid of vaccum tube 506. A suitable optical system 591, here represented by a converging lens, may be employed to direct the modulated light in a beam of essentially parallel rays for maximum effective distance of transmission and for maximum security against unwanted interception. Modulation of the light beam 5632 so produced, is used to effect control of the missile or airplane.

Fig. is a diagram of a circuit at the receiving station by means of which the modulated light beam from the transmitting system of Fig. 9 may be intercepted and converted into electrical signals which, in turn, may be separated and channeled to individual servomotors or other control actuating devices on the missile or controlled airplane. In the circuit of Fig. l0, the relationship between it and Fig. 2 is indicated by corresponding numerals with the letter d added. A converging lens 605 focuses the received light beam 6G upon the cathode surface of a photo-electric cell 660, which is here shown as a high-resistance, emissive type. Potential difference across the photo-electric cell 50B is maintained by the battery 56| which is connected in series with the load resistance 332. Incident light upon the cathode of the photo-electric cell 600 causes current to flow through the circuit just mentioned, and thus produces voltage drop across the resistor 392. The characteristics of the photoelectric cell employed should be such that changes of intensity of the incident light will produce proportional changes of potential drop across the load resistor 652. Under these conditions, the dynamic component of potential difference across the resistor 602 will be a reproduction of the modulation signal applied to the light beam at the transmitting station. This reproduced signal may be transferred through the blocking condenser B, the pre-amplifier 604 to the same lter circuits and subsequent circuits previously described in connection with Fig. 2. Such circuits govern the servomotors 75d to 18d, inclusive, in the manner previously described, for the purpose of actuating the controls on the missile or controlled airplane.

Fig. 11 has previously been described as an overall presentation of the remote control system disclosed herein.

Modifications may be made in the circuits and combinations disclosed herein without departing from the spirit of the inventiton, for example, the carrier wave transmitter or equivalent and the carrier wave receiver or equivalent may be eliminated from the combination. A wire connection would in such case run directly from the transmitter station to the receiver station and combine the transmitter and receiver to serve as a wired remote control system. Such a wire connection could be shown by a line connecting the outputof amplifier 503 of Fig. 9 with the input to preamplifier 6M of Fig. 10. For such use, the elements which would in the absence of the wire radiate and receive the carrier wave could then be eliminated.

The invention claimed is: i

l. A remote control system comprising, in combination, a transmitter having means for sending out simultaneously a plurality of variable amplitude radio wave signals differing in frequency from each other and adapted to bring about control apparatus pre-settings and a constant amplitude, constant frequency radio wave signal actuating a control; a multi-channelled radio receiving set on the object to be controlled, each channel but one in said set having means for converting one variable amplitude, constant frequency signal into relay settings accomplishing the desired result to be attained on Such object, relays adapted to be set by said signals, power means on said object for carrying out the changes established by said relay settings, and a channel on said receiving set connected to said power means for enabling said constant amplitude, constant frequency signal to energize said power means to accomplish the result in regard to the object that is established by said relay settings substantially as lsoon as said relay settings are completed.

2. A remote control system comprising, in combination, signal transmitting means for sending out simultaneously a plurality of variable voltage-amplitude radio wave signals differing in frequency from each other and a constant voltage-amplitude, constant frequency radio wave signal, a signal receiving means on an object to be controlled, including signal channeling means connected to said signal receiving means for isolating signals received from said transmitting means according to their individual frequencies, relay setting means in each channeling means responsive to the variable voltage-amplitude signal, relays adapted to be set by said signals, and power means for operating a control in response to said constant voltage-amplitude, constant frequency radio wave signal.

3. In a remote control system, a mobile controlled station mounted in an aircraft, and a control station, a television observation means and a television transmitter in said controlled station for transmitting a continuous view of the terrain about to be traversed by the controlled station, an instrument board in the controlled station adapted to give information of the conditions surrounding the operation of the controlled station, television observing and transmitting means for transmitting a continuous view of said instrument board, a wave energy receiving system in said controlled station whereby two signals of different frequency may be simultaneously received, controls proportionally actuable by said receiving system and signals whereby said controlled station may be guided, the control station including a pair of television receivers, a pilots seat and the conventional control stick and pedals of an airplane conventionally located in regard to said pilots seat, a pair of kinescopes forming a part of said television receivers, one giving a View of the terrain about to be traversed by the controlled station and the second giving a view of the instrument board in the controlledstation, each being located within close visual range of said pilots seat and a remote control transmitting system to which Said airplane control stick and pedals are operatively connected, said system having the power to control the receiving system within the mobile controlled station in accordance with the movement of the said conventional airplane controls at the control station.

4. In a receiving system for the remote control of a missile, airplane or the like, a receiver of signal transmitted from a remote point, channeling means associated with said receiver to separate the several components of a received signal according to their distinctive frequency characteristics, at least two channels of the said channeling means being responsive to reference signals and the remaining channels being responsive to control signals, at least two servomotors governed by each control channel, means for energizing and positioning one or another of said servomotors according to which one of the several reference channels is receiving signal and means in each control channel for energizing an electric circuit when signal is received in that control channel in the absence of signal receivable by the reference channels.

PAUL W. NOSKER.

REFERENCES CITED The following references are of record in the le of this patent:

26 UNITED STATES PATENTS Number Name Date 1,444,417 Hammond Feb. 6, 1923 2,006,440 Chireix July 2, 1935 2,039,405 Green et al, May 5, 1936 2,165,800 Koch July 11, 1939 2,184,075 Goldstein Dec. 19, 1939 2,204,438 Neufeld June 11, 1940 2,226,214 Albrecht Dec. 24, 1940 2,245,347 Koch June 10, 1941 2,256,487 Moseley et al Sept. 23, 1941 2,257,203 Thacker Sept. 30, 1941 2,339,257 Embiricos et al. Jan. 18, 1944 2,362,832 Land Nov. 14, 1944 2,382,709 Greene et al. Aug. 14, 1945 2,393,892 De Ganahl Jan. 29, 1946 2,397,088 Clay Mar. 26, 1946 2,397,477 Kellogg Apr. 2, 1946 2,408,819 Sorensen Oct. 8, 1946 2,446,279 Hammond Aug. 3, 1948 OTHERI REFERENCES R. C. A. Review, pages 293-302 (Flying Torpedo with an Electric Eye), September 1946.

Electronic Industries, pages 62-65 (Tele- Guided Missiles), May 1946.

Proceedings of the I. R. E., pages 375-401 (Television Equipment for Guided Missiles), June 1946. 

